Conventional small A. C. motor energizing circuits usually use (1) motor winding tap (as shown in FIG. 1) or (2) external serial electric reactance or resistance (as shown in FIGS. 2 and 3) or (3) a solid-state element (as shown in FIGS. 4 and 5) such as a power transistor or SCR as the speed control means to adjust the voltage or phase. The technique mentioned in item (1), causes trouble during winding and making the motor. Moreover, motors so constructed produce noises (especially at the medium speed due to the unbalance in the magnetic field). The approach described in item (2) increases the cost and results in heat losses, while the starting torque is lower. The use of solid-state elements described in item (3) has a higher cost and, when the power transistor adjusts the voltage, results in large heat losses. In the case where the SCR is used to adjust the phase, motor noises result and radio interference becomes a problem.